Damage analysis of CVI SiCf/SiCm ceramic matrix composites under thermal shock

Abstract

The low density, high strength, and excellent high-temperature resistance of ceramic matrix composites (CMCs) determine their significant application value in the extreme environments of advanced aero-engines. In this paper, the thermal shock performance and internal damage evolution of CMCs materials are investigated by X-ray computed tomography (XCT), infrared thermal imaging and acoustic emission (AE) non-destructive testing technologies. The results show that the silicon carbide (SiC) sealing coating on the chemical vapor infiltration – ceramic matrix ccomposites (CVI-CMCs) substrate is severely oxidized and peels off during the cyclic thermal shock process, resulting in exposure and damage to the fiber-reinforced phase and matrix phase. The k-means clustering results of the damage modes of CMCs materials during the thermal shock cycle test can be classified to four damage modes: fiber fracture (280–360 kHz), fiber/matrix crack propagation (225–270 kHz), interlayer spalling (125–165 kHz) and interface debonding or slipping between the fiber and matrix (80–115 kHz). Environmental barrier coatings (EBCs) can enhance the thermal shock resistance of CMC materials. After 900 thermal shock cycles, the peeling area of CVI-CMCs substrate coated with the EBCs is only 15 %, significantly lower than the 25 % observed in uncoated CVI-CMC substrate.